Inharmonicity

From AudioLexic

In music, inharmonicity is the degree to which the frequencies of the overtones of a fundamental differ from whole number multiples of the fundamental's frequency. These inharmonic overtones are often distinguished from harmonic overtones, all whole number multiples, by calling them partials, though partial may also be used to refer to both. Since the harmonics contribute to the sense of sounds as pitched or unpitched, the more inharmonic a sound the less definite it becomes in pitch. Many percussion instruments such as cymbals, tam-tams, and chimes, create complex and inharmonic sounds. Strings are more inharmonic the shorter and thicker they are, which becomes an important consideration for piano tuners, especially in the thick strings of the bass register; see Piano Acoustics.